Additional Strange Hadrons from QCD Thermodynamics and Strangeness Freezeout in Heavy Ion Collisions

Abstract

We compare lattice QCD results for appropriate combinations of net strangeness fluctuations and their correlations with net baryon number fluctuations with predictions from two hadron resonance gas (HRG) models having different strange hadron content. The conventionally used HRG model based on experimentally established strange hadrons fails to describe the lattice QCD results in the hadronic phase close to the QCD crossover. Supplementing the conventional HRG with additional, experimentally uncharted strange hadrons predicted by quark model calculations and observed in lattice QCD spectrum calculations leads to good descriptions of strange hadron thermodynamics below the QCD crossover. We show that the thermodynamic presence of these additional states gets imprinted in the yields of the ground-state strange hadrons leading to a systematic 5-8 MeV decrease of the chemical freeze-out temperatures of ground-state strange baryons.PACS numbers: 11.10. Wx, 11.15.Ha, 12.38.Gc, 12.38.Mh Introduction.-With increasing temperature the strong interaction among constituents of ordinary nuclear matter, mesons and baryons, results in the copious production of new hadronic resonances. The newly produced resonances account for the interaction among hadrons to an extent that bulk thermodynamic properties become well described by a gas of uncorrelated hadronic resonances [1]. The hadron resonance gas (HRG) model is extremely successful in describing the hot hadronic matter created in heavy ion experiments [2]. Abundances of various hadron species measured in heavy ion experiments at different beam energies are well described by thermal distributions characterized by a freeze-out temperature and a set of chemical potentials µ = (µ B , µ Q , µ S ) for net baryon number (B), electric charge (Q) and strangeness (S) [3]. Nonetheless, details of the freeze-out pattern may provide evidence for a more complex sequential freezeout pattern [4,5]. In particular, in the case of strange hadrons arguments have been put forward in favor of a greater freeze-out temperature than that of nonstrange hadrons [6][7][8].At the temperature T c = (154 ± 9) MeV [9] strong interaction matter undergoes a chiral crossover to a new phase. In the same crossover region HRG-based descriptions of the fluctuations and correlations of conserved charges for light [10], strange [6,11], as well as charm [12] degrees of freedom break down. Below T c , bulk thermodynamic properties as well as conserved charge distributions are generally well described by a HRG containing all experimentally observed resonances (PDG-HRG) listed in the particle data tables [13]. However, there are

QCD equation of state to O(μB6) from lattice QCD

“…In accordance with the analysis of the chiral transition temperature, T c (154±9) MeV [4], bulk thermodynamic observables change smoothly in the transition region. At low temperature they are found to be in quite good agreement with hadron resonance gas (HRG) model calculations, although some systematic deviations have been observed, which may be attributed to the existence of additional resonances which are not taken into account in HRG model calculations based on well established resonances listed in the particle data tables [5,6].…”

“…We therefore compare the QCD results also with a HRG model that includes additional strange baryons,which are not listed in the PDG but are predicted in quark models and lattice QCD calculations. We successfully used such an extended HRG model (QM-HRG) in previous calculations [5,6]. As can be seen in Fig.…”

Dynamical versus equilibrium properties of the QCD phase transition: A holographic perspective

“…The strangeness sector is especially interesting in light of the p/π puzzle at the LHC [85] where it has been suggested that there are possibly missing strange resonances when compared to Lattice QCD [86,87] and/or there could be a flavor hierarchy of chemical freeze-out temperatures [36,88]. Recent work [89] has also looked into the dynamics of strangeness and found that strange hadrons (with the exception of Λ's) generally freeze-out sooner than light hadrons.…”

Thermalization in a small hadron gas system and high-multiplicity pp events

“…The hadronic phase of the QCD medium is successfully addressed also by the Hadron Resonance Gas (HRG) Model [10][11][12], in statistical thermodynamic framework. An ideal HRG, formulated with discrete mass spectrum of * Electronic address: prem@vecc.gov.in identified hadrons and resonances, has been reinforced with the ab-initio confirmation [13][14][15][16] from the LQCD. Also, as yet unmeasured higher-mass hadron states, provided by the exponentially growing continuum mass spectrum, proposed [17] by R. Hagedorn, have important contribution to the equation of state (EoS) [18][19][20] below the critical temperature (T c ) for the QCD change of phase.…”